The order Cetacea includes the whales, dolphins and porpoises and comprise the mammals most fully adapted to aquatic life. It contains 81 known species organized in two suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales, which includes dolphins and porpoises). The order contains several record breaking species, with the Blue Whale being the largest animal known, and the Orca being the most widely distributed animal.
Cetaceans evolved from land mammals that adapted to marine life about 50 million years ago. Over a period of a few millions of years during the Eocene, the cetaceans returned to the sea. Their body is fusiform (spindle-shaped), the forelimbs are modified into flippers, the tiny hindlimbs are vestigial and the tail has horizontal flukes. Cetaceans are nearly hairless, and are insulated by a thick layer of blubber.
Cetaceans inhabit all of the world's oceans, as well as some rivers in South America and Asia. Some species can be found across the globe.
Cetology is the branch of marine science associated with the study of cetaceans.
Long and slender, the Blue Whale's body can be various shades of bluish-gray. There are at least three distinct subspecies: B. m. musculus of the north Atlantic and north Pacific, B. m. intermedia, of the Southern Ocean and B. m. brevicauda (also known as the Pygmy Blue Whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists mainly of small crustaceans known as krill, as well as small fish and squid.
26 August - Findings from the controversial Japanese whaling research program suggest that a loss of Antarctic sea ice due to increased temperatures has lowered whales' food supply, causing an overall decline in blubber. Read more...
...dolphins often leap clear of the water when travelling at speed. This is because the density of water is much greater than that of air and they are able to travel faster by leaping out of the water.
...whale and dolphin mothers ‘suckle’ their young underwater! Mothers have muscular mammary glands and ‘squirt’ their milk into the calf’s mouth, to ensure that the calf takes in as much of the energy rich milk as possible.
...on average, a whale or dolphin will eat four to five percent of its body weight in food per day. That means that a 100 ton blue whale will eat almost five tons of krill per day, or that a 200kg bottlenose dolphin will eat 10kg of fish per day!
...newborn cetacean calves ‘suckle’ three to four times each hour and will suckle from their mothers for six months or more.
Many whales are known to breach the waters surface. The act of leaping generates more power than any other act performed by a non-human animal.
Some whales, such as Sperm Whales, perform a breach by travelling vertically upwards from depth, and heading straight out of the water. Others, such as the Humpback Whale (pictured), travel close to the surface and parallel to it, and then jerk upwards at full speed to perform a breach. In a typical breach, as performed by a Humpback or Right Whale, the whale clears the water at an angle of about 30° to the horizontal.